@article {665, title = {Cutting floating single-walled carbon nanotubes with a {\textquoteleft}CO2 blade{\textquoteright}}, journal = {Carbon}, volume = {143}, year = {2019}, month = {Mar-2019}, pages = {481 - 486}, abstract = {

Uniform ultra-short (\< 100 nm) single-walled carbon nanotubes (SWCNTs) with properties of rich chemistry, high dispersity and easy manipulation, are of great importance for constructing novel nanostructures and highly integrated miniature devices. Herein, we report a recent breakthrough in cutting long SWCNTs into uniform ultra-short segments in gas-phase using CO2 as a \&$\#$39;blade.\&$\#$39; SWCNTs synthesized by an aerosol reactor are directly introduced into a second reactor for gaseous cutting. The quality and the number concentration of shortened SWCNTs are enhanced after the gas-phase cutting process. Moreover, the growth and cutting of SWCNTs are accomplished in a continuous gas-phase process, thus allows direct dry deposition of ultra-short SWCNTs as individual macromolecules or thin films onto various substrates for multiple applications. (C) 2018 Elsevier Ltd. All rights reserved.

}, issn = {00086223}, doi = {10.1016/j.carbon.2018.11.035}, url = {https://linkinghub.elsevier.com/retrieve/pii/S0008622318310558}, author = {Tian, Ying and Wei, Nan and Laiho, Patrik and Ahmad, Saeed and Yann Magnin and Liao, Yongping and Christophe Bichara and Jiang, Hua and Kauppinen, Esko I.} } @article {577, title = {Entropy-driven stability of chiral single-walled carbon nanotubes}, journal = {Science}, volume = {362}, year = {2018}, month = {Oct-12-2018}, pages = {212 - 215}, abstract = {

Single-walled carbon nanotubes are hollow cylinders that can grow centimeters long via carbon incorporation at the interface with a catalyst. They display semiconducting or metallic characteristics, depending on their helicity, which is determined during their growth. To support the quest for a selective synthesis, we develop a thermodynamic model that relates the tube-catalyst interfacial energies, temperature, and the resulting tube chirality. We show that nanotubes can grow chiral because of the configurational entropy of their nanometer-sized edge, thus explaining experimentally observed temperature evolutions of chiral distributions. Taking the chemical nature of the catalyst into account through interfacial energies, we derive structural maps and phase diagrams that will guide a rational choice of a catalyst and growth parameters toward a better selectivity.

}, issn = {0036-8075}, doi = {10.1126/science.aat6228}, url = {http://www.sciencemag.org/lookup/doi/10.1126/science.aat6228}, author = {Yann Magnin and Amara, Hakim and Ducastelle, Francois and Loiseau, Annick and Christophe Bichara} } @article {588, title = {From cellulose to kerogen: molecular simulation of a geological process}, journal = {Chemical Science}, volume = {8}, year = {2017}, month = {Dec-01-2017}, pages = {8325-8335}, abstract = {

The process by which organic matter decomposes deep underground to form petroleum and its underlying kerogen matrix has so far remained a no man\&$\#$39;s land to theoreticians, largely because of the geological (Myears) timescale associated with the process. Using reactive molecular dynamics and an accelerated simulation framework, the replica exchange molecular dynamics method, we simulate the full transformation of cellulose into kerogen and its associated fluid phase under prevailing geological conditions. We observe in sequence the fragmentation of the cellulose crystal and production of water, the development of an unsaturated aliphatic macromolecular phase and its aromatization. The composition of the solid residue along the maturation pathway strictly follows what is observed for natural type III kerogen and for artificially matured samples under confined conditions. After expulsion of the fluid phase, the obtained microporous kerogen possesses the structure, texture, density, porosity and stiffness observed for mature type III kerogen and a microporous carbon obtained by saccharose pyrolysis at low temperature. As expected for this variety of precursor, the main resulting hydrocarbon is methane. The present work thus demonstrates that molecular simulations can now be used to assess, almost quantitatively, such complex chemical processes as petrogenesis in fossil reservoirs and, more generally, the possible conversion of any natural product into bio-sourced materials and/or fuel.

}, issn = {2041-6520}, doi = {10.1039/C7SC03466K}, url = {http://xlink.rsc.org/?DOI=C7SC03466K}, author = {Atmani, Lea and Christophe Bichara and Roland Jean-Marc Pellenq and Henri Van Damme and Adri CT Van Duin and Raza, Zamaan and Truflandier, Lionel A. and Ama{\"e}l Obliger and Kralert, Paul G. and Franz-Josef Ulm and Jean-Marc Leyssale} } @article {410, title = {Magnetism as indirect tool for carbon content assessment in nickel nanoparticles}, journal = {Journal of Applied Physics}, volume = {122}, year = {2017}, month = {Jul-12-2017}, pages = {213902}, abstract = {

We report a combined experimental and theoretical study to ascertain carbon solubility in nickel nanoparticles embedded into a carbon matrix via the one-pot method. This original approach is based on the experimental characterization of the magnetic properties of Ni at room temperature and Monte Carlo simulations used to calculate the magnetization as a function of C content in Ni nanoparticles. Other commonly used experimental methods fail to accurately determine the chemical analysis of these types of nanoparticles. Thus, we could assess the C content within Ni nanoparticles and it decreases from 8 to around 4\ at. \% with increasing temperature during the synthesis. This behavior could be related to the catalytic transformation of dissolved C in the Ni particles into graphite layers surrounding the particles at high temperature. The proposed approach is original and easy to implement experimentally since only magnetization measurements at room temperature are needed. Moreover, it can be extended to other types of magnetic nanoparticles dissolving carbon.

}, issn = {0021-8979}, doi = {10.1063/1.5006138}, url = {http://aip.scitation.org/doi/10.1063/1.5006138http://aip.scitation.org/doi/pdf/10.1063/1.5006138}, author = {Oumellal, Y. and Yann Magnin and {\'\i}nez de Yuso, A. and Aguiar Hualde, J. M. and Amara, H. and Paul-Boncour, V. and Matei Ghimbeu, C. and Malouche, A. and Christophe Bichara and Roland Jean-Marc Pellenq and Zlotea, C.} } @article {248, title = {Fracture toughness anomalies: Viewpoint of topological constraint theory}, journal = {Acta Materialia}, volume = {121}, year = {2016}, month = {Dec-2016}, pages = {234 - 239}, abstract = {

The relationship between composition, structure, and resistance to fracture remains poorly understood. Here, based on molecular dynamics simulations, we report that sodium silicate glasses and calcium\–silicate\–hydrates feature an anomalous maximum in fracture toughness. In the framework of topological constraint theory, this anomaly is correlated to a flexible-to-rigid transition, driven by pressure or composition for sodium silicate and calcium\–silicate\–hydrates, respectively. This topological transition, observed for an isostatic network, is also shown to correspond to a ductile-to-brittle transition. At this state, the network is rigid but free of eigen-stress and features stress relaxation through crack blunting, resulting in optimal resistance to fracture. Our topological approach could therefore enable the computational design of tough inorganic solids, which has long been a \“holy grail\” within the non-metallic materials chemistry community.

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}, issn = {13596454}, doi = {10.1016/j.actamat.2016.09.004}, author = {Mathieu Bauchy and Wang, Bu and Wang, Mengyi and Yu, Yingtian and Mohammad Javad Abdolhosseini Qomi and Smedskjaer, Morten M. and Christophe Bichara and Franz-Josef Ulm and Roland Jean-Marc Pellenq} } @article {131, title = {Rigidity transition in materials: hardness is driven by weak atomic constraints.}, journal = {Phys Rev Lett}, volume = {114}, year = {2015}, month = {Mar-23-2015}, pages = {Article Number: 125502}, abstract = {

Understanding the composition dependence of the hardness in materials is of primary importance for infrastructures and handled devices. Stimulated by the need for stronger protective screens, topological constraint theory has recently been used to predict the hardness in glasses. Herein, we report that the concept of rigidity transition can be extended to a broader range of materials than just glass. We show that hardness depends linearly on the number of angular constraints, which, compared to radial interactions, constitute the weaker ones acting between the atoms. This leads to a predictive model for hardness, generally applicable to any crystalline or glassy material.

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}, issn = {1079-7114}, doi = {10.1103/PhysRevLett.114.125502}, author = {Mathieu Bauchy and Mohammad Javad Abdolhosseini Qomi and Christophe Bichara and Franz-Josef Ulm and Roland Jean-Marc Pellenq} } @article {115, title = {Nanoscale Structure of Cement: Viewpoint of Rigidity Theory}, journal = {Journal of Physical Chemistry C}, volume = {118}, year = {2014}, month = {Jun-12-2014}, pages = {12485-12493}, type = {Article}, abstract = {
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Rigidity theory is a powerful tool to predict the properties of glasses with respect to composition. By reducing such molecular networks to simple mechanical trusses, topological constraint theory filters out all the unnecessary details that ultimately do not affect macroscopic properties. However, the usual constraint enumeration is restricted to networks that are amorphous, homogeneous, and fully connected. On the contrary, calcium\–silicate\–hydrate (C\–S\–H), the binding phase of cement, is partially crystalline and heterogeneous and shows some isolated water molecules. Here, we report how rigidity theory can be used to describe the nanoscale structure of this material by relying on molecular dynamics simulations. The distinction between intact and broken constraints is clearly defined at the atomic scale, thus allowing a precise enumeration of the topological constraints. We show that the rigidity of the C\–S\–H network can be increased by decreasing the Ca/Si molar ratio, which, as predicted by rigidity theory, allows improvement of the hardness of the material. This study suggests that rigidity theory could be applied with great rewards to a broader range of materials than glasses.

}, issn = {1932-7447}, doi = {10.1021/jp502550z}, author = {Mathieu Bauchy and Mohammad Javad Abdolhosseini Qomi and Christophe Bichara and Franz-Josef Ulm and Roland Jean-Marc Pellenq} } @article {58, title = {Structure and properties of nanoscale materials: theory and atomistic computer simulation}, journal = {International Journal of Nanotechnology}, volume = {9}, year = {2012}, month = {2012}, pages = {576{\textendash}604}, abstract = {

We present a review of a few research topics developed within the \"Theory and Atomistic Computer Simulation\" Department at CINaM. The bottom line of the scientific activity is to use up\–to\–date theoretical and computer simulation techniques to address physics and materials science problems, often at the nanometric scale, in close contact with experimental groups. It ranges from the study of the structure and properties of molecular systems for organic electronics to metallic clusters and alloys, magnetic oxides, nuclear fuels and carbon\–based nanostructures. These studies are motivated by fundamental research questions as well as more applied goals including environmental and energy issues, or information technologies. This broad spectrum of activities requires a large range of techniques, from theory and ab initio calculations to semi\–empirical models incorporated in Monte Carlo or molecular dynamics simulations.

}, doi = {10.1504/IJNT.2012.045335 }, author = {Christophe Bichara and Marsal, P and Mottet, C and Roland Jean-Marc Pellenq and F. Ribeiro and Andres Sa{\`u}l and G. Tr{\'e}glia and Weissker, H{\textendash}Ch} } @article {288, title = {Tight binding within the fourth moment approximation: Efficient implementation and application to liquid Ni droplet diffusion on graphene}, journal = {Physical Review B}, volume = {84}, year = {2011}, month = {Aug-31-2011}, pages = { Article Number: 085455}, abstract = {

Application of the fourth moment approximation (FMA) to the local density of states within a tight binding description to build a reactive, interatomic interaction potential for use in large scale molecular simulations, is a logical and significant step forward to improve the second moment approximation, standing at the basis of several, widely used (semi-)empirical interatomic interaction models. In this paper we present a sufficiently detailed description of the FMA and its technical implications, containing the essential elements for an efficient implementation in a simulation code. Using a recent, existing FMA-based model for C-Ni systems, we investigated the size dependence of the diffusion of a liquid Ni cluster on a graphene sheet and find a power law dependence of the diffusion constant on the cluster size (number of cluster atoms) with an exponent very close to \−2/3, equal to a previously found exponent for the relatively fast diffusion of solid clusters on a substrate with incommensurate lattice matching. The cluster diffusion exponent gives rise to a specific contribution to the cluster growth law, which is due to cluster coalescence. This is confirmed by a simulation for Ni cluster growth on graphene, which shows that cluster coalescence dominates the initial stage of growth, overruling Oswald ripening.

}, issn = {1098-0121}, doi = {10.1103/PhysRevB.84.085455}, author = {Los, J. H. and Christophe Bichara and Roland Jean-Marc Pellenq} }